How do you keep your nerve when prong-setting a brittle stone?

The hesitation is normal, honestly. If you've ever snapped anything along a cleavage, you never forget it, and beryl will do it to you. I set aquas all the time and I still slow way down on that first prong.

Here's what changed everything for me on fragile stones: don't close any prong fully on the first pass. Seat the stone, then go around all of them giving each one just a tiny nudge, barely enough to see contact. Repeat around three or four times, tightening a little each pass. Going opposite prongs first and closing them hard is exactly how you get uneven side-load on the girdle, and that's usually the crack. The gentle-sequence method keeps the stone centered and the pressure even, so it works the same for the tourmaline.

Pusher angle matters more than people say. You want the push coming straight down onto the prong, toward the bearing face, so the metal folds over the crown rather than dragging sideways across it. A sideways shove is what pops chips off. Also check your seat depth. The girdle should sit just slightly proud of where the prong tip meets it, so the prong folds over the stone instead of grabbing at the edge. Shallow bearing cuts like you did are right, just make sure the seat itself is flat and even, not scooped.

On warming the prongs, I think it's mostly folksy advice. A little heat can make platinum marginally less springy but platinum dumps heat badly and you'd need more warmth than is safe to get a real change. I skip it. What actualy helps me is a grooved pusher and fresh control. Any wobble in the tool transfers straight to the stone. Also, if your hands freeze up mid-close, stop and walk away. Half-closed prongs hold the stone fine overnight. Nothing wrong with finishing this one tomorrow.

Been setting beryls since before anyone here was born prolly, and one old habit from my apprenticeship still holds up. My bench boss made me cut the seats, then check them by seating the stone and pressing on it with a wax stick. If it rocks or sits crooked you fix the seat, not the prongs. Most cracked aquas I saw over the years were really bad seats hiding under a careful prong job. Also I still use a plain wooden pusher on anything soft. Slips less than steel, and you can feel the metal move. The old guys had it right on that one.

One thing that helps my nerves on stones like this, I cut a thin strip of wax paper and lay it over the crown while I do the first pass. You can still see the girdle line through it and it stops a slip of the pusher from glancing straight into the stone. Took it off a jeweler I watched work a 6 carat morganite years back and I've used it on every fragile stone since. Also agree the tourmaline first is the right call, green ones are tougher than people give them credit for but no reason to gamble on which one you crack.

The wax paper trick above is a good one, I do something similar with a thin cork pad under my bench pin so any tap transfers less shock. What really calmed my nerves on fancy stones was practicing on cheap CZs set in scrap mounts first. Spend an evening snapping a few $2 stones on purpose and suddenly the real one doesn't feel so scary. You learn exactly how much pressure it takes before things go bad, which is weirdly reassuring. Does anyone else rehearse like that or am I just weird?

Update: the wax paper trick got me through the tourmaline last night, first prong went way smoother than usual. Still frozen on the aqua though. For the person who said press the stone with a wax stick to check the seat, do you do that before you ever touch a prong, or after you've got the first couple closed?